Development of a Procedure for Calculating the Surface Properties of Binary Solid Solutions with Regard to the Ordering of Components

Abstract

An approach to calculating the surface energy and the surface tension in solid–vapor systems of binary solid solutions with different degrees of ordering is developed based on the lattice gas model (LGM). The LGM is the only procedure allowing a uniformly accurate description of the properties of phases and transition regions between the coexisting equilibrium phases. The model is targeted at mixture components with comparable sizes. It is adapted for the simplest type of ordering in a bulk phase, which reflects the structure of two interpenetrating sublattices in a simple cubic lattice or a body-centered cubic lattice of β-brass type. The transition region between a solution and vapor is presented as a multilayered region with a variable density of components. Interatomic interaction potentials are taken into account in the approximation of pair contributions with maintaining direct correlation effects. To reduce the system of equations for the distribution of components, a change of variables is applied, which makes it possible to bring the problem to the dimensionality of concentration profiles of components in the transition region. The procedure that has been developed allows the evaluation of the interface roughness state, the specific surface of the rough surface, and the segregation of solution components, as well as an analysis of the effect of their surface segregation on the degree of ordering of solution components in the transition region.